Despite a host of chances for both sides, it looked like Viborg and Brondby were headed for a share of the spoils when an injury-time match-winning goal gave Brondby all three points in the away fixture against Viborg.
Thanks to the 1-0 win, Brondby enters the equation as a possible contender for the bronze medals.
There is now only a three-point gap to FC Nordsjaelland in third place before they take on AGF on Thursday.
Substitute Dennis turned match-winner when he hammered a rebound into the roof of the goal after a wild scramble in Viborg's box.
It would also have been completely misleading if the match had ended without goals, as the spectators in Viborg were treated to great entertainment and lots of action in both boxes.
Brondby already had the ball over the line in the first minute, but Nicolai Vallys used his hand in the process, so the goal was disallowed.
Brondby coach Steve Cooper had re-selected the same 11 players who started in the 6-0 win against Sonderjyske on Friday. But the team apparently had used up most of its goal quota in that match.
Midway through the first half, Viborg goalkeeper Lucas Lund was forced to make a strong double save to prevent Jacob Ambaek and Nicolai Vallys from putting the away team ahead.
And in the next minute, Viborg's Lukas Kirkegaard hit the post with a header, while Jeppe Gronning headed the rebound over the bar.
Vallys also failed to score when he had the first chance of the second half. His header was parried by Lucas Lund, as the two teams continued to challenge each other.
Viborg's Charly Nouck missed the target by inches with a terrific volley after an hour, and with fifteen minutes left, Brondby's hat-trick hero from the Sonderjyske match, Jacob Ambæk, turned and twisted his way into the Viborg box but squared his effort wide of the target.
In injury time, Lucas Lund saved two Brondby attempts following a goalmouth scramble, but the ball fell kindly for Emmanuel Dennis, who decided an entertaining match.